In manufacturing processes of a circuit board, after forming electrically conductive patterns on a board, it is required to inspect the presence of disconnection and/or short-circuit in the conductive patterns.
As for such an inspection technique, a contact type inspection technique has been heretofore known in which a conductive pattern was subjected to a continuity check or the like by bringing two separate pins into contact with the opposed ends of the conductive pattern to apply an electric signal from one of the two pins to the conductive pattern and then receive the electric signal through the other pin.
However, recent progressive densification in the conductive patterns makes it difficult to bring the pins into contact with each of the conductive patterns from point to point precisely. Thus, a non-contact type inspection method has been proposed in which no pin was used at the receiving side and the electric signal was received without contacting the conductive pattern.
In this non-contact type inspection technique, a pin to be contacted to the conductive pattern is placed at one end of the conductive pattern, and a sensor is placed adjacent to the other end of the conductive pattern in a non-contact manner. Then, an electric signal having temporal variations is supplied to the pin, and a corresponding electric signal which appears at the sensor after passing through the capacitance lying between the conductive pattern and the sensor is detected to inspect the disconnection and others of the conductive pattern.
In the above technique, an inspection chip serving as the sensor is generally mounted on a package formed of an insulating material.
FIG. 15 is a schematic plan view showing a structure of a conventional inspection apparatus 100. FIG. 16 is a sectional view taken along the line X—X of FIG. 15.
The inspection apparatus 100 comprises a package 101, an inspection chip 102 mounted on the package 101, and an insulative film 104 provided on the surface of the inspection chip 102.
The package 101 includes a plurality of leads 101a each connected to a corresponding electrode pad 102a of the inspection chip 102 through a bonding wire 103. An associated device including a computer uses the leads 102 to communicate with the inspection chip 102. For example, the computer for controlling the inspection apparatus 100 inputs a control signal into the inspection chip 102 through the leads 101a and detects a signal from the inspection chip 102 through the leads 101a. 
The inspection chip 102 is fixedly mounted within a recessed portion 101b of the package 101 with an adhesive or the like, and the inspection surface of the inspection chip 102 (the upper surface of the inspection chip 102 in FIG. 16) is arranged to be exposed outside the recessed portion 101b. A circuit board 200 as an inspection object is placed opposed to the inspection surface and above the top surface of the inspection apparatus 100.
In order to detect a signal from a conductive pattern of the circuit board 200 sufficiently, the film 104 protects the inspection surface of the inspection chip 102 and fills a gap between the circuit board 200 and the inspection chip 102, to provide a higher dielectric constant therebetween than that of an air layer otherwise existing.
On the other hand, as a desirable technique for obtaining an adequate signal from the conductive pattern, it is known to minimize the distance between the inspection surface of the inspection chip 102 and the conductive pattern, i.e., to dispose the inspection surface possibly close to the conductive pattern. Thus, in a design for packaging the inspection chip 102 to the package 101, the inspection surface of the inspection chip 102 is desirably exposed out of the inspection apparatus 100 as much as possible.
However, the conventional inspection apparatus 100 is involved with the problem in design that the inspection surface of the inspection chip 102 cannot be disposed sufficiently close to the conductive pattern as an inspection object, due to the bonding wire 103 for connecting the electrode pads 102a of the inspection chip 102 with the leads 101a of the package 101. This is caused by the necessity that the bonding wire 103 is bent not to contact the peripheral portion of the inspection chip 102. The above problem will be described with reference to FIG. 17, which shows a detail structure around the bonding wire 103 of FIG. 16.
The bonding wire 103 is partially formed in a chevron shape having a height h1 to provide a distance between the peripheral portion of the sensor chip 102 and the bonding wire 103. In this case, the electrode pads 102a and the bonding wire 103 are bonded with each other by an ultrasonic thermo-compression bonding process. In the course of this process, the bending strength of the bonding wire 103 is degraded by a eutectic reaction between a material (typically aluminum) of the electrode pads 102a and a material (typically gold) of the bonding wire 103. Thus, the height h1 is required to be about 150 mm or more to avoid bending failure.
As a result, it is required to provide a distance of at least the height h1 between the inspection surface of the inspection chip 102 and the circuit board 200. Additionally, a certain margin is necessary for avoiding an accidental interference between the top of the bonding wire 103 and the circuit board 200. Consequently, it will be necessary to provide a distance h2 (>h1) between the inspection surface of the inspection chip 102 and the circuit board 200.
Thus, the conventional inspection apparatus 100 has been involved with the problem in design that the inspection surface of the inspection chip 102 cannot be disposed sufficiently close to the conductive pattern.
Further, in order to obtain an adequate signal from the conductive pattern, during an operation of the inspection apparatus 100, the inspection apparatus 100 is desirably hold to allow the inspection surface of the inspection chip 102 to be arranged approximately in parallel with the conductive pattern.
It is therefore an object of the present invention to provide an inspection apparatus and a holder thereof, which allows the inspection chip to be positioned adequately to the conductive pattern as an inspection object.